Transcript Slide 1

What is Klinefelter
syndrome?
Klinefelter's syndrome is a
condition that occurs in men who
have an extra X chromosome
contained in their sex chromosomes.
The syndrome can affect different
stages of physical, language, and
social development.
Discovery of
Klinefelter Syndrome
In 1942, Dr. Harry Klinefelter and his
coworkers first described the combination
of features that has come to be recognized
as Klinefelter Syndrome. By the late 1950's,
researchers discovered that men with this
group of symptoms had an extra sex
chromosome, XXY instead of the usual
male arrangement of XY.
What are the genetic changes
related to Klinefelter syndrome?
Klinefelter syndrome is a condition related
to the X and Y chromosomes (the sex
chromosomes). Most often, Klinefelter
syndrome results from the presence of one
extra copy of the X chromosome in each cell
(47,XXY). Extra copies of genes on the X
chromosome interfere with male sexual
development, often preventing the testes from
functioning normally and reducing the levels of
testosterone.
Variants vs. Mosaic
• Some people with features of Klinefelter syndrome have more
than one extra sex chromosome in each cell (for example,
48,XXXY or 49,XXXXY). These conditions, which are called
variants of Klinefelter syndrome, tend to cause more severe
signs and symptoms than classic Klinefelter syndrome. In
addition to affecting male sexual development, variants of
Klinefelter syndrome are associated with intellectual disability,
distinctive facial features, skeletal abnormalities, poor
coordination, and severe problems with speech. As the number
of extra sex chromosomes increases, so does the risk of these
health problems.
• Some people with features of Klinefelter syndrome have the
extra X chromosome in only some of their cells; in these
individuals, the condition is described as mosaic Klinefelter
syndrome (46,XY/47,XXY). Individuals with mosaic Klinefelter
syndrome may have milder signs and symptoms, depending
on how many cells have an additional X chromosome.
Symptoms
• Affected individuals typically have small testes that do not
produce as much testosterone as usual. Testosterone is the
hormone that directs male sexual development before birth and
during puberty. A shortage of testosterone can lead to delayed or
incomplete puberty, breast enlargement, reduced facial and body
hair, and an inability to have biological children. Some affected
individuals also have genital differences also.
• Older children and adults with Klinefelter syndrome tend to be
taller than their peers. Compared with unaffected men, adults
with Klinefelter syndrome have an increased risk of developing
breast cancer and chronic inflammatory diseases.
• Children with Klinefelter syndrome may have learning disabilities
and delayed speech and language development. They tend to be
quiet, sensitive, and unassertive, but personality characteristics
vary among affected individuals.
Can Klinefelter syndrome
be inherited?
Klinefelter syndrome and its variants are not
inherited; these chromosomal changes usually
occur as random events during the formation of
reproductive cells in a parent. An error in cell
division called nondisjunction results in a
reproductive cell with an abnormal number of
chromosomes. For example, an egg or sperm cell
may gain one or more extra copies of the X
chromosome as a result of nondisjunction. If one of
these atypical reproductive cells contributes to the
genetic makeup of a child, the child will have one
or more extra X chromosomes in each of the
body's cells.
How common is
Klinefelter syndrome?
• Klinefelter syndrome affects 1 in 750
newborn males. Most variants of
Klinefelter syndrome are much rarer,
occurring in 1 in 50,000 or fewer
newborns.
• Researchers suspect that Klinefelter
syndrome is underdiagnosed because
the condition may not be identified in
people with mild signs and symptoms.
Additionally, the features of the condition
vary and overlap significantly with those
of other conditions.
Diagnosis of Klinefelter Syndrome
• Klinefelter syndrome may first be diagnosed
when a man comes to the doctor because of
infertility. Infertility is the most common
symptom. Karyotyping, semen counts, and
blood tests to check hormone levels may also
be performed for diagnosis.
Treatment Options
• Testosterone therapy can be prescribed
for treatment. This can help:
– Grow body hair
– Improve appearance of muscles
– Improves mood and self esteem
– Increase energy and strength